Skinny Physics for QS&BB

Author

Chip Brock

Published

September 12, 2025

1 Introduction to Skinny Physics

I’m guessing that you might come from various backgrounds and since posts in QS&BB may rely on a small bit of background, I’ve created this Skinny Physics collection to help you whether you’re an humanities major with little physics in your past life or an engineer with more.

1.1 The approach

To follow my posts and to appreciate particle physics you don’t need a whole textbook, you need a friend. My approach in Skinny Physics is to present some facts and weave worked-out examples among them. Most of these will have relevance for my articles and some might just be for fun and connection with your life.

I have a confession: in Engineering School I had a professor who taught a course in Systems Engineering and he never once gave a lecture. From the first day to the last he worked out examples. Each tied to the ones before and when strung together…well, it was a whole narrative, soup to nuts.

I don’t think I need to do that here, but you’ll find examples that should take you quickly through a concept. Learning or remembering. Same result.

So few words, and lots of examples

1.2 Chapter structure

Each chapter has the same structure in support of your particular level of preparation:

  1. Different way. There are some places where I introduce ways of approaching things in QSBB that you wouldn’t have seen elsewhere. So follow those links for sure.
  2. Just the facts. The equations for those of you who might have had some physics in your background and need a referesher
  3. Gentle explanations of... This is textbook-like, but textbook-lite. From the beginning but not overpowering. Lots of written examples. Some videos examples.
  4. Pointers to topics so you can quickly go to a topic where you need more than just the equations. That’s #4 just above 👆

The Parts are:

  1. Mechanics
    1. Motion
    2. Momentum and Force
    3. Collisions
    4. Energy
  2. Gravitation
    1. Copernicus’ heliocentric proposal
    2. Galileo’s Astronomy
    3. Kepler’s Astrophysics
    4. Newton’s Gravitation
  3. Electricity and Magnetism
    1. Electric Charge and Magnetism
    2. Faraday’s Experiments and Conclusions
    3. Maxwell’s Theory
    4. Forces on electrical charges
  4. Einstein’s Theory of Special Relativity

1.3 Some important definitions and my conventions:

I’ll use:

  • A subscript “0” for any quantity that is meant to be the beginning of a process or sequence of events:
  • \(x_0\) to be where we start in distance
  • \(x\) (no subscript) to be where we end up (sometimes, I’ll be explicit and say “\(x_f\)” for “final.”)
  • We’ll use the Greek symbol Delta, \(\Delta\) to mean “change of”…this will come up a lot.
  • change in position is \(\Delta x = x_{\text{ended up}}-x_{\text{where we started}} = x-x_0\)
  • same goes for time, from \(\Delta t= t_{\text{ended up}}-t_{\text{when we started}} = t - t_0\)
  • the symbol for average: \(\bar{A}\) or \(\langle A\rangle\)
  • the symbol for the (nearly) constant acceleration due to gravity close to the Earth’s surface: \(g\), aka “little gee”
  • Space and time are going to be our friends. If time doesn’t march on, we’ve not moved. But what is time? “Tubby…paused. ‘Time,’ he added slowly – ’time is what keeps everything from happening at once…”1 We’ll see time take on a new meaning.

  1. This is often attributed to Einstein, Woody Allen, and John Wheeler! It actually comes from Ray Cummings’ short story The Time Professor from 1921. Stick with me. You’ll learn all sorts of odd facts.↩︎